Rheumatoid factor is not only seen in patients with rheumatoid arthritis, but also in other autoimmune diseases, chronic infectious diseases, and even in some normal healthy people, especially the elderly. A positive rheumatoid factor is not in itself diagnostic of rheumatoid arthritis. This is because rheumatoid factor is not only seen in patients with rheumatoid arthritis, but also in people with many other diseases and even in healthy people. A negative rheumatoid factor does not rule out rheumatoid arthritis either. Because: 1, not all rheumatoid patients rheumatoid factor is positive, rheumatoid patients rheumatoid factor positive rate of 50% to 90%; 2, routine rheumatoid factor test negative, may be part of the recessive rheumatoid factor; 3, some patients after a period of time, rheumatoid factor can be negative to positive. The correlation between rheumatoid factor and rheumatoid arthritis disease: in general, seronegative rheumatoid patients have lighter synovitis and less extra-articular manifestations; on the contrary, seropositive rheumatoid patients, especially those with high titers of rheumatoid factor, are more likely to have progressive and erosive arthritis with loss of joint function, and are prone to extra-articular manifestations such as necrotizing vasculitis and rheumatoid nodules, with poor long-term The prognosis is poor.